In an upset, Elizabeth Warren ousts Massachusetts Sen. Scott Brown

WASHINGTON – Elizabeth Warren defeated Massachusetts Sen. Scott Brown in a marquee race for a seat that was crucial to Republican hopes of gaining control of the Senate.

It was one of the most-watched campaigns of the year, with Warren, the Democrats’ consumer activist icon, against Brown, the Republican who shocked everyone in 2010 when he won the seat that had been occupied for decades by the late Sen. Edward M. Kennedy.

In a year in which most races across the country had featured Democrats casting Republicans as extremists, this one turned that narrative on its head.

On Tuesday, the Associated Press and NBC called the race for Warren.

Brown had anticipated a tough challenge from the moment he won the seat in a special election to replace Kennedy. In his short time in the Senate, he built a record as a moderate pragmatist designed to appeal to voters in his solid blue state.

It was Warren who came across as the radical. A Harvard law professor best known for her role as the chief architect of the Consumer Financial Protection Bureau -- a watchdog agency created by the Dodd-Frank financial reform law -- Warren became the Democrats’ fiercest voice for liberal economic theory.

“There is nobody in this country who got rich on his own, nobody,” Warren said last August as she was contemplating her Senate bid. “You built a factory out there? Good for you. But I want to be clear: You moved your goods to market on the roads the rest of us paid for, you hired workers the rest of us paid to educate, you were safe in your factory because of police forces and fire forces that the rest of us paid for.”

Obama would later echo those comments, prompting attacks from Republican Mitt Romney.

Warren’s economic approach turned out to be the least of the controversies in the race. Many months were spent instead discussing Warren’s supposed Native American heritage, after it was revealed that she had identified herself as a minority professor in a law faculty directory but did not have proof of the 1/32 Cherokee heritage that she claimed.

The campaign was also notable for its lofty – if flawed – attempt to restrict the flood of money from unlimited spending by outside groups. In an unusual move last January, Warren and Brown signed a pact that if outside groups spent money advertising on behalf of one of the candidates, that candidate would have to dip into campaign funds to make a donation to the charity of their opponent’s choice. The amount would be equal to half of what was spent by the outside group.

Some groups tested the candidates’ sincerity and ran ads anyway. Brown made nearly $37,000 in donations to charities as a result.

But by and large, the pact was successful at limiting the barrage of attack ads on the airwaves. Still, outside groups found a loophole that allowed them to spend freely on direct mail. The pact only covered advertising on television, radio and online.

As a result, Massachusetts residents were inundated with mailers from groups like Grover Norquist’s Americans for Tax Reform, the AFL-CIO and the League of Conservation Voters. One super PAC, America 360 Committee, spent $1.2 million on mailers to help Brown, according to data compiled by the Center for Responsive Politics.

In total, outside groups spent about $6.5 million, but the real spending came from the candidates’ own committees. By mid-October, they had spent a combined $66 million. Brown had spent slightly more -- $36 million compared to Warren’s $30 million.